1. Field of the Invention
The field of this invention is in off road, ground engaged vehicles.
2. Related Art
Non-construction and non-agricultural off road vehicles include various classes of designs including what are popularly known as “all terrain vehicles” and “utility vehicles.” These types of off road vehicles face a variety of challenges in covering terrain. Most of these challenges are related to obstacles, objects and/or soft ground in the path of travel that can stop the vehicle's progress. Meeting and overcoming these obstacles is more successful to the extent that the following characteristics can be optimized: lowering the center of gravity; increasing power; maintaining traction; maintaining stability; maximizing ground clearance; maximizing maneuverability; and, when necessary, easing maintenance. As always, controlling cost is a continuing need in the art.
Most vehicles in the all terrain vehicle (ATV) and utility vehicle (UV) classes have suspensions systems similar to the familiar automobile suspension systems and constructed and arranged with springs and shock absorbers and the like. The design of said systems allows an individual wheel to travel vertically relative to the rest of the vehicle in order to ride over an obstacle while the rest of the vehicle proceeds past the obstacle. The problem with such suspension systems is that the vehicle body as a whole does not increase its ground clearance when it is most needed—when a large obstacle is to be overcome. Hence, when an obstacle is large enough, a sprung wheel may flex vertically to accommodate it, but the ground clearance of the body of the vehicle will still be stopped by the obstacle. There is a need in the art for a vehicle that will increase the ground clearance of its entire body in order to overcome larger or rougher obstacles.
Further, during the time that an individual sprung wheel is flexing vertically to avoid an obstacle, traction is lost with that wheel, and the constant application of power to the ground by that wheel is lost. Hence, there is also a need in the art for an off road vehicle that continues to apply constant traction and power to the ground while obstacles are overcome.
Prior art ATVs and UVs, having conventional drive systems with the mechanical linkages between an internal combustion engine and the wheels, typically including a transmission and differential, further complicating the constant delivery of power and traction to the ground by the wheels in rough terrain. There is a need in the art for a drive system that increases power, maintains traction through all four wheels at all times and affords higher torque in a slower wheel spin.
There is a further need in the art for a vehicle whose maneuverability is maximized in order to travel in and through narrow spaces between insurmountable obstacles. Accordingly, there is a need in the art for a vehicle with four wheel steering.
Hydrostatic drive and hydrostatic motors mounted directly on the wheels are known, but not generally in off road vehicles. Skid steers and fork trucks used in warehousing are often driven by hydrostatic motors mounted directly to individual wheels. The advantage of such drive systems is very low wheel spin rates and the maintenance of high torque at extremely low speeds, thereby allowing increased maneuverability in close quarters, especially while maneuvering a load. It is not known to apply pure hydrostatic drive technology to off road vehicles. Accordingly, there is a need in the art for the maximized maneuverability and torque at low speeds afforded by hydrostatic drives as applied here thereto unapplied to off road vehicle technology.